Energy is can be transmitted through or reflected from a medium to determine characteristics of the medium. For example, in the medical field, instead of extracting material from a patient's body for testing, light or sound energy may be caused to be incident on the patient's body and transmitted (or reflected) energy may be measured to determine information about the material through which the energy has passed. This type of non-invasive measurement is more comfortable for the patient and can be performed in real time.
Non-invasive physiological monitoring of bodily functions is often required. For example, during surgery, blood pressure and the body's available supply of oxygen, or the blood oxygen saturation, are often monitored. Measurements such as these are often performed with non-invasive techniques where assessments are made by measuring the ratio of incident to transmitted (or reflected) light through a portion of the body, for example a digit such as a finger, or an earlobe, or a forehead.
Demand has increased for disposable and reusable optical probes which are suitably constructed to provide low-noise signals to be output to a signal processor in order to determine the characteristics of the medium. Many difficulties relating to motion-induced noise have been encountered in providing such an optical probe inexpensively. A need thus exists for a low-cost, low-noise optical probe and for a method of efficient manufacturing such a probe.